It's a Great Time to Go for a Drive

In an era when Apple charges 99 cents per month for 50GB of iCloud storage and Google offers 100GB of free storage for two years with the purchase of a new Chromebook, mainstream external hard drives might appear less essential than they once were.

But modern external drives are faster, more stylish, and often more durable than their counterparts from a few years ago. They're ever cheaper and more capacious, too. For about $50, you can add a terabyte of extra storage to your laptop or desktop by just plugging in a USB cable.

Choosing an external drive isn't as simple as buying the most expensive one you can afford, however. The capacity and type of storage mechanism are the two most important factors to consider, and each one will increase or decrease the cost dramatically depending on your needs. Other factors include the physical size of the drive (is it designed to be carted around or to sit on your desk?), how rugged it is, the interface it uses to connect to your PC, and even what colors it comes in. This guide will help you make sense of all the options. Here are the key questions to ask as you shop.

The Need for Speed: Hard Drive or SSD?

Solid-state drives (SSD) have fewer moving parts than a traditional hard drive, and they offer the speediest access to your data. Unlike a conventional disk-based hard drive, which stores data on a spinning platter or platters accessed by a moving magnetic head, an SSD uses a collection of flash cells—similar to the ones that make up a computer's RAM—to save data. (For an in-depth look at exactly how this cell-based storage works, check out this tech explainer from sister site ExtremeTech.)

Just how much faster is it to access data stored in flash cells than those stored on a spinning platter? Typical read and write speeds for consumer drives with a single spinning platter are in the 100MBps to 200MBps range, depending on their USB interface and whether they spin at 5,400rpm (more common) or 7,200rpm (more expensive and less common). External SSDs offer twice that speed and sometimes much more, with typical results on our benchmark tests in excess of 400MBps. Practically speaking, this means you can move gigabytes of data (say, a 4GB feature-length film, or a year's worth of family photos) to your external SSD in seconds rather than the minutes it would take with an external spinning drive.

Not only is it faster to read and write data stored in flash cells than those stored on a spinning platter, but it's also safer. Because there is no spinning platter or moving magnetic head, if you bump the SSD while you're accessing its data, there is no risk that your files will become corrupted and unreadable.

While external SSDs are now readily available and cheaper than they were a few years ago, they're not a complete replacement for spinning drives. Larger external drives designed to stay on your desk or in a server closet still mostly use spinning drives, taking advantage of their higher capacities and lower prices compared with SSDs. Want to know more about how hard drives and SSDs compare? Check out our explainer SSD vs. HDD: What's the Difference?

Physical Size Matters: Desktop or Portable Drive?

If you have a large photo or video collection—perhaps you are a photo or video editor, or maybe a movie buff—you'll likely need several terabytes of space in which to store it. So your best option is a desktop-class drive. We define these as having one or more spinning-platter drives inside and requiring its own dedicated power cable. Of course, in this scenario, your files are going to have to stay at your desk.

A desktop drive with a single platter mechanism inside will typically use a 3.5-inch drive inside and will be found in capacities up to 12TB, and most are roughly 5 inches tall and 2 inches wide. In addition to storing large media collections, these drives can also serve as inexpensive repositories for backups of your computer's hard drive that you schedule using either the software that came with the drive or a third-party backup utility.

The next size up for consumer desktop drives is about the same height but twice as wide to accommodate additional drive mechanisms in the chassis, such as with the Western Digital My Book Duo. These larger drives are more expensive but also much more capacious; the highest-capacity current models employ two drives for up to 20TB of storage. Note: In the case of these and single-platter-drive products, you're not meant to swap out the drive or drives inside.

The largest desktop drives are often much, much larger than the first two categories, so large that you'll want to stick them under your desk or in a dedicated server closet. They're mostly intended for professional use in editing studios, surveillance control rooms, and the like. Their defining characteristic is the ability to swap drives in and out easily, so they provide quick access to the drive bays at the front of the device. Most are sold without drives included, so you can install any drive you want (usually, 3.5-inch drives, but some support 2.5-inchers). Their total storage capacities are usually limited only by their number of available bays and the capacities of the drives you put in them.

At the other end of the physical-size spectrum are portable drives, some of which now use an SSD inside instead of a spinning platter to save space, as well as to increase throughput and durability. These drives can be truly tiny, weighing just a few ounces and with their largest sides measuring less than 3 inches long, like with the Samsung Portable SSD T5. Others use spinning platters and are a bit larger, like the LaCie Porsche Design Mobile Drive, but they still fit easily in a purse or even a coat pocket. Portable drives get their power from the computer to which you connect them, through the interface cable, so there's no need for a spare wall outlet.

Need Redundancy or Extreme Speed? Consider a RAID

If you buy a larger desktop drive with two or more spinning platters, you'll almost certainly have the ability to configure the drive as a RAID array using included software. Depending on which RAID level you choose, you can prioritize capacity, speed, or data redundancy, or some combination thereof.

A collection of spinning drives configured with a RAID level designed for faster access can approximate the speeds of an SSD, while you should consider a drive with support for RAID levels 1, 5, or 10 if you're storing really important data that you can't afford to lose. Hit the link above for explanation of the strengths of each RAID level.

What Interface Should You Look For?

How an external drive connects to your PC or Mac is second only to the type of storage mechanism it uses in determining how fast you'll be able to access data. Unfortunately, these connection types are constantly changing, and the internet is littered with outdated references to legacy interface types such as eSATA and FireWire.

Right now, the fastest mainstream connection type is Thunderbolt 3, which is handy assuming you have a newer laptop or desktop with a Thunderbolt 3 port. All late-model Apple laptops have them, but they're much scarcer on Windows machines. This interface uses a USB Type-C connector and offers blazing throughput of 40GBps. As an added bonus, a desktop drive that supports Thunderbolt 3 might also come with additional DisplayPort and USB connections that allow you to use the drive box as a hub for your keyboard, mouse, monitor, and other peripherals.

You'll really only see the speed benefits of Thunderbolt 3, however, if you have a drive that's SSD-based, or a RAID array. If you'd rather save money than time transferring your data, if you're buying a desktop drive with a single platter-based mechanism inside, or if you have a PC that lacks Thunderbolt 3, you'll want to make sure your drive has a USB 3.0 connection. Nearly every recent drive we reviewed supports USB 3.0, and the same goes for laptops and desktops.

And of course, if you're carrying your drive around with you, you want it to look nice. Some, like the Samsung T5, come in multiple colors, while others, like the ADATA SD700, are super-slim and ready to be tossed in a pocket.

Perhaps the only thing you don't need to pay much attention to is the warranty. If your drive breaks because you damaged it, the warranty likely won't cover it. Even if the drive fails because of a manufacturing defect, most warranties simply replace the drive and don't cover the cost of recovery services that attempt to rescue your data from the broken drive.

Let's Look at the Top Models We've Tested...

Also know that you can find external drives that do way more than just store your data. Some include SD card readers to offload footage from a camera or drone in the field, while others have built-in Wi-Fi and can double as an all-in-one home media server. (See our roundup of the best wireless hard drives and SSDs.) Some of that kind even come with extra-large batteries that can charge your smartphone while you're on the go.

Bottom Line: The 1-terabyte Buffalo MiniStation Extreme NFC has a built-in cable you can't lose, a rugged chassis that will survive a rough daily commute, and an NFC card and reader add some security to this portable hard drive.

About the Author

Joel Santo Domingo is the Lead Analyst for the Desktops team at PC Magazine Labs. He joined PC Magazine in 2000, after 7 years of IT work for companies large and small. His background includes managing mobile, desktop and network infrastructure on both the Macintosh and Windows platforms. Joel is proof that you can escape the retail grind: he wore a yellow polo shirt early in his tech career. Along the way Joel earned a BA in English Literature and an MBA in Information Technology from Rutgers University. He is responsible for overseeing PC Labs testing, as well as formulating new test methodologies for the PC Hardware team. Along with ... See Full Bio